Electric Propulsion Orientation Control for Axle Battery Balancing
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Solution Overview
Problem
Heavy-duty electric working machines with separate electric systems for each axle often experience uneven battery discharge, leading to premature charging stops as the rear axle batteries drain faster than front axle batteries, especially when driving uphill or downhill with poor traction.
Innovation Solution
A computer system that determines the longitudinal gradient and charge levels of both electric energy storage systems, adjusting the working machine's orientation to balance charge levels by controlling which axle leads during uphill or downhill segments, ensuring the axle with lower charge provides less power during uphill travel and recovers energy for charging during downhill travel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate electric systems are provided for each axle, then each axle can be independently powered, but the battery packs discharge unevenly causing premature charging stops
Solution Approach 1:
The system dynamically adjusts the orientation of the working machine based on real-time charge levels of the battery packs and the gradient of the terrain. The control system switches between first orientation (first axle leading) and second orientation (second axle leading) to balance the discharge rates of the separate electric systems, preventing premature charging stops.
Solution Approach 2:
The system changes the operational parameter of machine orientation based on the state of charge of the battery packs. When one battery pack's charge level drops below a threshold, the system switches orientation to reduce the load on that battery pack, thereby balancing the discharge rates and extending the overall operating range.
2Power
If the working machine travels uphill in the first orientation, then the first electric system provides more power, but the first battery pack discharges faster
Solution Approach 1:
Instead of always traveling uphill in the first orientation, the system inverts the approach by switching to the second orientation (second axle leading) when the first battery pack's charge level is low. This allows the second electric system to provide the necessary uphill power while the first battery pack recharges or discharges at a slower rate.
3Reliability
If the working machine changes orientation frequently, then charge levels can be balanced, but the control system complexity increases
Solution Approach 1:
The control system continuously monitors the charge levels of both battery packs and the machine's current orientation. When the charge level difference between the two battery packs exceeds a predetermined threshold, the system triggers an orientation switch. This feedback mechanism ensures charge balance while maintaining relatively simple control logic.
Data Source
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AI summary
A computer system (400) and a method for control of an electric propulsion system (200) of an autonomous working machine (100) comprising a first axle (110) and a second axle (120), the electric propulsion system comprising: - a first electric system (210) configured to drive the first axle, comprising a first electric energy storage system (211a, 211b), - a second electric system (220) configured to drive the second axle, comprising a second electric energy storage system (221a, 221b). The method comprises: - determining a longitudinal gradient along an expected travelling path, - determining charge levels of the first and second electric energy storage systems, respectively, - controlling the working machine to assume a first orientation or a second orientation to travel along the expected travelling path, wherein the orientation of the working machine is controlled in dependence on the determined longitudinal gradient and the determined charge levels.